DESCRIPTION (provided by application): Active surveillance of acute gastroenteritis (AGE) will be conducted in the Emergency Dept. and in hospitalized patients who are seen at Children's Hospital & Research Center, Oakland (Oakland, CA), with the aims of determining the burden of AGE, the burden of rotavirus AGE, and the burden of norovirus AGE in children 15 days to <10 years of age. Clinical, demographic, and vaccination information will be collected for each patient. A stool sample will be collected from each patient within 14 days of onset of AGE symptoms. Stool samples will be tested on site by enzyme immunoassay (EIA), to detect rotaviruses. Stool samples will be tested for noroviruses by real-time polymerase chain reaction (RT-PCR). All stool samples demonstrating a positive result will be forwarded to CDC, for serotyping. Saliva samples will be obtained in a portion of AGE cases for determination of norovirus-secretor status. Age-matched children with acute respiratory infection (ARI) will be assigned for rotavirus cases, and age-matched normal children will be assigned for norovirus AGE cases. Population-based incidence rates by age will be determined for each of the following: total AGE, RV AGE and norovirus AGE, in hospitalized patients as well as patient seen only in the ED.